In order to increase the competitiveness of future mobile networks, the 3rd generation partnership project (3GPP) is researching a future network architecture. The network architecture includes an SAE at a network side and an evolved universal terrestrial radio access network (E-UTRAN) (i.e. LTE) at a wireless side. The structure of an evolved packet system (EPS) is as shown in FIG. 1, and includes at least three logical function entities, i.e., a mobility management entity, a serving gateway, and a packet data network gateway. The mobility management entity is in charge of mobility management of control-plane, which includes management of user context and mobility status, temporary user identity assignment, security function, etc. The serving gateway is a mobile anchor point for local inter base station handover and inter 3GPP access system handover, and is in charge of managing and storing IP bearer parameters and network routing information, lawful interception, etc. The packet data network gateway is a gateway towards the external network, and is in charge of realizing policy-based management, user-based packet filtering, accounting, lawful interception, user IP address assignment, etc., and therefore serves as a user-plane anchor point among different access systems. Subscription information of users is stored in a home subscriber server (HSS).
A protocol used for an interface between the serving gateway and the packet data network gateway may be the general packet radio service (GPRS) tunneling protocol (GTP), or the proxy mobile IP protocol (PMIP).
Although manners for establishing connections by using different protocols are defined in different transfer services (TS) respectively, in a process of practical network deployment and upgrade, the serving gateway may support multiple connection protocols (for example, the GTP and the PMIP) at the same time, while the packet data network gateway only supports one of them (for example, the GTP). Under this situation, a connection between the serving gateway and the packet data network gateway is usually established by using the following manners.
The serving gateway uses one connection protocol to initiate a connection establishment request to the packet data network gateway. When the packet data network gateway does not support such a protocol, no response is received. After timeout, the serving gateway considers to use another connection protocol again to initiate the connection establishment request. When implementing the present invention, the inventor discovers a disadvantage of such a manner: if the connection protocol selected by the serving gateway first time is a connection protocol not supported by the packet data network gateway, a time delay when the connection is established successfully will be extended.
Or, the serving gateway may use multiple protocols supported by the serving gateway at the same time to initiate the connection establishment request to the packet data network gateway. The packet data network gateway selects one or all of the protocols for responses according to its own ability. The serving gateway selects one response message that first reaches to establish a connection. When implementing the present invention, the inventor of the present invention discovers a disadvantage of such a manner: for a serving gateway that supports multiple protocols, more processing is required. Also, such a mechanism that a sender sends multiple messages of the same function but with different protocols regardless of the ability of the receiver will consume more processing resources.